A collagen-platelet composite has been developed and validated by the investigators in a canine model to heal partial ACL tears both biomechanically and histologically. Further, the platelet collagen device has been shown in a porcine model to promote ACL repair. The change to the canine model is advantageous to evaluate our device in a known clinically relevant ACL injury, repair, reconstruction model. This model will allow evaluation for development of osteoarthritis (OA), validated gait/lameness scores, arthroscopic inspection of the knee, comparison of biomechanical results and histology to known standards, and has the potential to control rehabilitation in the future. Further, the huge size of adult, skeletally mature porcine and the limitations on supply and expense of the "minipig" are avoided, thus reducing cost of evaluation of this device. The PI has extensive experience with canine knees with ACL reconstruction, meniscus injury models, osteochondral allograft and autograft procedure in addition to partial ACL tear model (biomechanical and histological healing with our device). The proposed study has the following Aims. Aim 1: Evaluate the clinical function of healing collagen-platelet composite ACL repair by validated canine lameness score. Hypothesis 1: The lameness scores will decrease over four to twelve weeks with successful healing and be associated with less medial meniscus tears and chondromalacia on medial femoral condyle and medial tibial plateau at euthanasia. Our goal is met when 80% <lameness of 3. Aim 2: Delineate the effects of the collagen-platelet composite on knee joint laxity (anteroposterior/axial) after 12 weeks of healing. Hypothesis 2: The AP laxity values of the ACL repair knees treated with the concentrated collagen-platelet composite will be within range of postoperative laxity seen after ACL reconstructions (~250% of the intact contralateral knee). Our goal is met by 80% achieving this value. Aim 3: Measure the structural properties (maximum load to failure/linear stiffness) and histology (cellularity/vascularity) of the healing ACL repair with collagen-platelet composite after 12 weeks. Hypothesis 3: The structural properties of the ACL repairs treated with a collagen-platelet composite will be greater than 20% of intact contralateral ACL. Our goal is met by 80% achieving this value. The PI and investigators have the required expertise and resources to evaluate this promising novel device for an innovative ACL repair in a known clinically relevant canine knee ACL model. Ten canines will undergo unilateral ACL repair and be evaluated clinically (lameness and intraarticular pathology), joint laxity, and structural properties of healing ACL repair. The contralateral normal knee will serve as control and prior completed canine and porcine experiments (ACL repair, reconstruction, and deficient) by this investigative team will serve as historical controls. Successful completion of Phase I will be defined by a priori established criteria for intact repair, AP laxity, load at yield, lameness and meniscus status at 12 weeks. PUBLIC HEALTH RELEVANCE: Over 300,000 ACL reconstructions (ACLRs) are performed each year at an estimated cost to the U.S. health system of $2.5 billion a year. Use of our proprietary Collagen Platelet Composite with primary repair will significantly reduce procedure time and rehabilitation time, eliminate complications and morbidity associated with graft harvesting, and preserve the broad insertion sites and proprioceptive function of the native ACL, which will dramatically cut the pain and lost productivity of reconstruction surgery. Preliminary estimates show that repair with our technology can save the U.S. health system over $1 billion in direct cost and substantially more in indirect costs by regaining thousands of person-years of lost productivity.